Evaluation of Morphed Human Body Models for Diverse Occupant Safety Analysis

Licentiate thesis, 2020

Female, obese, and elderly occupants are at increased risk of injury in vehicle accidents. Human Body Models (HBMs) are used to represent the human anatomy and to study injury mechanisms in mathematical crash test simulations. HBM morphing methods can adjust the anatomical geometry of existing HBMs, enabling HBMs to represent the diverse occupant population, beyond the traditionally considered body sizes.

The aims of this thesis were to define and select a diverse population of occupants. Thereafter, select an HBM morphing tool for morphing of the SAFER HBM to individuals in this population; Finally, this population of morphed HBMs was to be validated.

The defined target population to be represented by HBMs in occupant injury risk evaluations included individuals of both sexes. The selection was based on occupant injury risks and biomechanical risk factors. The male and female sub-populations include individuals of a wide range of statures and weights and ages from 20 to 80 years. A sample of 27 female and 27 males were selected as the initial population.

The parametric HBM morphing tool, developed by University of Michigan Transportation Research Institute, was selected for morphing the SAFER HBM.

Sled test results from individual male and female Post Mortem Human Subjects (PMHSs) of a wide range of body sizes were used for validation of morphed HBMs.

The SAFER HBM was parametrically morphed to each individual PMHS. Predictions from both morphed and the baseline SAFER HBM were collected in reconstructions of the PMHS tests. HBM kinematics, chest deflections and interaction forces were compared to corresponding test results using CORA cross-correlation rating. Comparison of morphed and baseline HBM results showed that correlation rating was not consistently improved for morphed HBMs. For large, obese, and small female subjects in frontal impacts, and in lateral impacts, morphed HBMs were stiffer than the corresponding PMHSs.  

To improve morphed SAFER HBM predictions for diverse occupants, future work will identify and mitigate the sources of the stiff responses through model updates. Sex and age dependent biomechanical properties, as available in literature will be included.

Biofidelity criteria for morphed HBMs will be defined and with morphed HBMs meeting these criteria, protective principles increasing the protection of all occupants will be investigated.